Characterising Mycobacterium tuberculosis Rv1510c protein and determining its sequences that specifically bind to two target cell lines

Mammalian cell cultures as models for Mycobacterium tuberculosis-human immunodeficiency virus (HIV) interaction studies: A review

Mycobacterium tuberculosis and human immunodeficiency virus (HIV) co-infections have remained a major public health concern worldwide, particularly in Southern Africa. Yet our understanding of the molecular interactions between the pathogens has remained poor due to lack of suitable preclinical models for such studies. We reviewed the use, this far, of mammalian cell culture models in HIV-MTB interaction studies. Studies have described the use of primary human cell cultures, including (1) monocyte-derived macrophage (MDM) fractions of peripheral blood mononuclear cell (PBMC), alveolar macrophages (AM), (2) cell lines such as the monocyte-derived macrophage cell line (U937), T lymphocyte cell lines (CEMx174, ESAT-6-specific CD4(+) T-cells) and an alveolar epithelial cell line (A549) and (3) special models such as stem cells, three dimensional (3D) or organoid cell models (including a blood-brain barrier cell model) in HIV-MTB interaction studies. The use of cell cultures from other mammals, including: mouse cell lines [macrophage cell lines RAW 264.7 and J774.2, fibroblast cell lines (NIH 3T3, C3H clones), embryonic fibroblast cell lines and T-lymphoma cell lines (S1A.TB, TIMI.4 and R1.1)]; rat (T cells: Rat2, RGE, XC and HH16, and alveolar cells: NR8383) and primary guinea pigs derived AMs, in HIV-MTB studies is also described. Given the spectrum of the models available, cell cultures offer great potential for host-HIV-MTB interactions studies.

Rv1268c protein peptide inhibiting Mycobacterium tuberculosis H37Rv entry to target cells

Tuberculosis (TB) remains one of the most worrying infectious diseases affecting public health around the world; 8.7 million new TB cases were reported in 2011. The search for an Mycobacterium tuberculosis H37Rv protein sequence which is functionally important in host-pathogen interaction has been proposed for developing a new vaccine which will allow efficient and safe control of the spread of this disease. The present study thus reports the results obtained for the Rv1268c protein described in the M. tuberculosis H37Rv genome as a hypothetical unknown, probably secreted, protein based on a highly robust, specific, sensitive and functional approach to the search for potential epitopes to be included in an anti-tuberculosis vaccine. Rv1268c presence was determined by immunoblotting after obtaining polyclonal sera against mycobacterial total sonicate or subcellular fractions. Such sera were used in electron immunomicroscopy (EIM) for confirming protein localisation on the M. tuberculosis envelop by recognising colloidal gold-labelled immunoglobulin. Screening assays revealed the presence of two sequences having high binding activity: one binding A549 alveolar epithelial cells ((141)TGMAALEQYLGSGHAVIVSI(160)) and other binding U937 monocyte-derived macrophages ((21)AVALGLASPADAAAGTMYGD(40)). Such sequences' ability to inhibit mycobacterial entry during in vitro assays was analysed. The structure of synthetic peptides binding to target cells was also determined, bearing in mind the structure-function relationship. These results, together with those obtained for other proteins, have been involved in selecting peptides which might be included in a subunit-based anti-tuberculosis vaccine.

Mycobacterium tuberculosis surface protein Rv0227c contains high activity binding peptides which inhibit cell invasion

Mycobacterium tuberculosis surface proteins involved in target cell invasion may be identified as a strategy for developing subunit-based, chemically-synthesized vaccines. The Rv0227c protein was thus selected to assess its role in the invasion and infection of Mycobacterium tuberculosis target cells. Results revealed Rv0227c localization on mycobacterial surface by immunoelectron microscopy and Western blot. Receptor-ligand assays using 20-mer, non-overlapping peptides covering the complete Rv0227c protein sequence revealed three high activity binding peptides for U937 phagocytic cells and seven for A549 cells. Peptide 16944 significantly inhibited mycobacterial entry to both cell lines while 16943 and 16949 only managed to inhibit entrance to U937 cells and 16951 to A549 cells. The Jnet bioinformatics tool predicted secondary structure elements for the complete protein, agreeing with elements determined for such chemically-synthesized peptides. It was thus concluded that high activity binding peptides which were able to inhibit mycobacterial entry to target cells are of great importance when selecting peptide candidates for inclusion in an anti-tuberculosis vaccine.

The Mycobacterium tuberculosis membrane protein Rv0180c: Evaluation of peptide sequences implicated in mycobacterial invasion of two human cell lines

The identification and characterization of hypothetical membrane proteins from Mycobacterium tuberculosis have led to a better understanding of the mechanisms used by this pathogen to invade and survive inside host cells. This study assessed the presence, transcription, localization and possible biological activity of the conserved hypothetical protein Rv0180c from M. tuberculosis. Bioinformatics analyses indicated that Rv0180c contains a signal peptide, six possible transmembrane helices and a Plasmodium Export Element (PEXEL)-like motif. PCR analyses showed the presence of the Rv0180c gene in strains from the M. tuberculosis complex; but transcription was not detected in Mycobacterium microti. Sera against synthetic peptides of Rv0180c recognized two protein bands in M. tuberculosis H37Rv sonicate: a ∼48-kDa band close to the predicted molecular mass of Rv0180c (47.6 kDa), and a 63-kDa band probably caused by protein modifications. Moreover, the same sera located the protein on the surface of M. tuberculosis H37Rv bacilli by immunoelectron microscopy. Twenty-three synthetic peptides spanning the entire length of Rv0180c were tested for their ability to bind to U937 and A549 cells, finding nine high-activity binding peptides (HABPs) specific for both cell types, two HABPs specific for A549 cells (namely 31032 and 31044) and two HABPs specific for U937 cells (namely 31025 and 31041). HABPs inhibited invasion of M. tuberculosis H37Rv into A549 or U937 cells by significant percentages and facilitated internalization of latex beads in A549 cells. The Rv0180c HABPs herein reported could be preliminary candidates to be assessed as components of a multiepitope, chemically synthesized, subunit-based vaccine against tuberculosis.

Peptides from the Mycobacterium tuberculosis Rv1980c protein involved in human cell infection: insights into new synthetic subunit vaccine candidates

Mycobacterium tuberculosis infection continues to be a major cause of morbidity and mortality throughout the world. The vast complexity of the intracellular pathogen M. tuberculosis and the diverse mechanisms by which it can invade host cells highlight the importance of developing a fully protective vaccine. Our vaccine development strategy consists of including fragments from multiple mycobacterial proteins involved in cell invasion. The aim of this study was to identify high activity binding peptides (HABPs) in the immunogenic protein Rv1980c from M. tuberculosis H37Rv with the ability to inhibit mycobacterial invasion into U937 monocyte-derived macrophages and A549 cells. The presence and transcription of the Rv1980c gene was assessed in members belonging to the M. tuberculosis complex and other nontuberculous mycobacteria by PCR and RT-PCR, respectively. Cell surface localization was confirmed by immuno-electron microscopy. Three peptides binding with high activity to U937 cells and one to A549 cells were identified. HABPs 31100, 31101, and 31107 inhibited invasion of M. tuberculosis into A549 and U937 cells and therefore could be promising candidates for the design of a subunit-based antituberculous vaccine.

Mycobacterium tuberculosis Rv0679c protein sequences involved in host-cell infection: potential TB vaccine candidate antigen

Background

To date, the function of many hypothetical membrane proteins of Mycobacterium tuberculosis is still unknown and their involvement in pathogen-host interactions has not been yet clearly defined. In this study, the biological activity of peptides derived from the hypothetical membrane protein Rv0679c of M. tuberculosis and their involvement in pathogen-host interactions was assessed. Transcription of the Rv0679c gene was studied in 26 Mycobacterium spp. Strains. Antibodies raised against putative B-cell epitopes of Rv0679c were used in Western blot and immunoelectron microscopy assays. Synthetic peptides spanning the entire length of the protein were tested for their ability to bind to A549 and U937 cells. High-activity binding peptides (HABPs) identified in Rv0679c were tested for their ability to inhibit mycobacterial invasion into cells.

Results

The gene encoding Rv0679c was detected in all strains of the M. tuberculosis complex (MTC), but was only transcribed in M. tuberculosis H37Rv, M. tuberculosis H37Ra and M. africanum. Anti-Rv0679c antibodies specifically recognized the protein in M. tuberculosis H37Rv sonicate and showed its localization on mycobacterial surface. Four HABPs inhibited invasion of M. tuberculosis to target cells by up to 75%.

Conclusions

The results indicate that Rv0679c HABPs and in particular HABP 30979 could be playing an important role during M. tuberculosis invasion of host cells, and therefore could be interesting research targets for studies aimed at developing strategies to control tuberculosis.

Peptides derived from the Mycobacterium tuberculosis Rv1490 surface protein implicated in inhibition of epithelial cell entry: potential vaccine candidates?

This study reports the Rv1490 gene presence and transcription in members of the Mycobacterium tuberculosis complex, and characterises the encoded Rv1490 putative membrane protein in M. tuberculosis H37Rv. Rv1490 derived peptides were synthesised and their A549 and U937 cell binding ability was tested, finding five high activity binding peptides (HABPs) for A549 and five for U937. Only two HABPs (11060 and 11073) were shared by both cell lines, both of which affected M. tuberculosis' invading ability to target cells, thus indicating an important role for these sequences in M. tuberculosis entry to A549 alveolar epithelial cells and supporting their inclusion in further studies on the development of a subunit-based multi-epitopic, chemically synthesised anti-tuberculosis vaccine.

Characterizing the Mycobacterium tuberculosis Rv2707 protein and determining its sequences which specifically bind to two human cell lines

The Rv2707 gene encoding a putative alanine- and leucine-rich protein was found to be present in all Mycobacterium tuberculosis complex strains (by PCR) and its transcription was shown by RT-PCR in all but M. bovis and M. microti. Antibodies raised against Rv2707 peptides specifically recognized the native protein by Western blot and were able to locate this protein on the M. tuberculosis membrane by immunoelectron microscopy. A549 and U937 cells lines were used in binding assays involving synthetic peptides covering the whole Rv2707 protein. High A549 cell-binding peptide 16083 (281 QEEWPAPATHAHRLGNWLKAY 300) was identified. Peptides 16072 (61 LFGPDTLPAIEKSALSTAHSY 80) and 16084 (301 RIGVGTTTYSSTAQHSAVAA 320) presented high specific binding to both A549 and U937 cells. Cross-linking assays revealed that peptide 16084 specifically bound to a 40-kDa and a 50-kDa U937 cell membrane protein. High activity binding peptides (HABPs) 16083 and 16084 were able to inhibit M. tuberculosis invasion of A549 cells. Our results suggest that these sequences could be part of the binding sites used by the bacillus for interacting with target cells, and thus represent good candidates to be tested in a future subunit-based, multiepitope, antituberculosis vaccine.

Identifying putative Mycobacterium tuberculosis Rv2004c protein sequences that bind specifically to U937 macrophages and A549 epithelial cells

Virulence and immunity are still poorly understood in Mycobacterium tuberculosis. The H37Rv M. tuberculosis laboratory strain genome has been completely sequenced, and this along with proteomic technology represent powerful tools contributing toward studying the biology of target cell interaction with a facultative bacillus and designing new strategies for controlling tuberculosis. Rv2004c is a putative M. tuberculosis protein that could have specific mycobacterial functions. This study has revealed that the encoding gene is present in all mycobacterium species belonging to the M. tuberculosis complex. Rv2004c gene transcription was observed in all of this complex's strains except Mycobacterium bovis and Mycobacterium microti. Rv2004c protein expression was confirmed by using antibodies able to recognize a 54-kDa molecule by immunoblotting, and its location was detected on the M. tuberculosis surface by transmission electron microscopy, suggesting that it is a mycobacterial surface protein. Binding assays led to recognizing high activity binding peptides (HABP); five HABPs specifically bound to U937 cells, and six specifically bound to A549 cells. HABP circular dichroism suggested that they had an alpha-helical structure. HABP-target cell interaction was determined to be specific and saturable; some of them also displayed greater affinity for A549 cells than U937 cells. The critical amino acids directly involved in their interaction with U937 cells were also determined. Two probable receptor molecules were found on U937 cells and five on A549 for the two HABPs analyzed. These observations have important biological significance for studying bacillus-target cell interactions and implications for developing strategies for controlling this disease.